This invention relates to apparatus and method for transferring liquids, and more particularly to centrifugal pump apparatus and method for transferring raw materials, materials in the state of manufacture, and finished products, in liquid form or in a liquid mixture or suspension, as well as for services relating to water supply, boiler feed, condenser circulation, and condensate return.
It is well known that the centrifugal pump is the type most widely used in the chemical industry for transferring liquids. The primary advantages of a centrifugal pump are simplicity, low cost, uniform non-pulsating flow, small floor space, low maintenance, and quiet operation. In its simplest form, the centrifugal pump consists of an impeller rotating within a casing. The impeller consists of a number of blades mounted on a shaft that projects outside the casing. The casing consists of a chamber in which the impeller rotates and is provided with an inlet and an outlet for the liquid being pumped. Power from an outside source is applied to the shaft thus rotating the impeller within the stationary casing. In revolving, the impeller produces a reduction in pressure causing liquid to flow into the impeller from the inlet, and forced from the outlet at an increased tangential velocity which is changed to pressure head at the outlet of the pump.
However well the performance of a centrifugal pump, special problems of sealing the centrifugal pump are inherent. Since a rotating shaft is displaced radially when in operation in varying amounts depending upon the load transmitted, seals must be provided to prevent leakage. Current practice demands that packing boxes be constructed to accommodate both packing and mechanical seals. However, the use of packing results in the continuous escape of a small amount of liquid past the seal since its operation depends upon the maintenance of wetted surfaces to minimize heat generation. Mechanical seals, on the other hand, cannot be adjusted without shutting down the pump for maintenance.
This invention relates to an improved pumping apparatus in the form of a solenoid-actuated centrifugal pump. The preferred embodiment is in the form of a closed duct having an iron core impeller propelled therein by means of a solenoid and wherein movement of the iron core impeller within the duct does not necessitate the need for supporting seals, bearings, or packings, and thus avoiding the complex and cumbersome constructions inherent in prior art pumps of the centrifugal type.
There is depicted and described in U.S. Pat. No. 2,915,973, one or more embodiments of a sealess centrifugal-type pump having an arcuately shaped liquid conducting conduit closed except for an inlet and an outlet, and with magnets movable along the conduit. Liquid metal enters the arcuate conduit and the movement of the magnets along the conduit creates forces which act on the liquid metal in the conduit and move the liquid metal through the conduit. The pump of U.S. Pat. No. 2,915,973, will convey liquid and without employing seals, packing, and bearings, for the pump housing. On the other hand, the pump of said patent is subject to disadvantages that limit its practical value. In the first place, it is effective for pumping liquid metal but is completely useless for pumping any other non-conductive liquid. In the second place, it relies upon externally mounted magnets as the driving force and does not contain within the fluid conducting conduit itself any impeller for increasing the tangential velocity of the liquid therein.
These disadvantages of the prior art, and especially the aforementioned U.S. Pat. No. 2,915,973, are overcome with the present invention, and commercially acceptable embodiments of a centrifugal pump and the like are herein provided which are not only fully capable of pumping liquids under most operating conditions but which are also fully capable of other tasks completely beyond the capabilities of the pump of the aforesaid patent, such as pumping non-conductive liquids. More particularly, however, the embodiments of the present invention are capable of operation with a much higher efficiency.